1. Field of the Invention
The present invention relates generally to the closure of intravascular defects and more specifically to a device for closing a cardiovascular or cardiac septal defect, the device being made of a polymeric material delivered to the site of the defect by a catheter and hardened in-situ to a predetermined configuration to function as a plug.
2. General Background
The normal heart is divided into four chambers, the two upper being the left and right atria and the two lower being the left and right ventricles. The atria are separated from each other by a muscular and a membranous wall, the interatrial septum, and the ventricles by the interventricular septum.
Either congenitally or by acquisition, abnormal openings, holes or shunts can occur between the chambers of the heart or the great vessels (interatrial and interventricular septal defects or patent ductus arteriosus and aortico-pulmonary window respectively), causing shunting of blood through the opening. The deformity is usually congenital, resulting from a failure of completion of the formation of the septum, or wall, between the two sides during fetal life when the heart forms from a folded tube into a four-chambered, two unit system.
These deformities can carry significant sequelae. For example, with an atrial septal defect, blood is shunted from the left atrium of the heart to the right, producing an overload of the right heart. In addition to left-to-right shunts such as occur in patent ductus arteriosus from the aorta to the pulmonary artery, the left side of the heart has to work harder because some of the blood which it pumps will recirculate through the lungs instead of going out to the rest of the body. The ill effects of these lesions usually cause added strain on the heart as well as the lungs which ultimately causes failure of the lungs and/or heart.
Previously, intracardiac septal defects and extracardiac pathologic vascular communications have required surgical intervention. To date the most common method of closing intracardiac shunts, such as atrial-septal defects and ventricular-septal defects, involves an intracardiac (open heart) operation requiring a sternotomy or a thoracotomy and diversion of the blood from the heart with the use of a cardiopulmonary bypass. The heart is then opened, the defect is sewn shut by direct suturing with or without a patch of synthetic material (usually of Dacron, teflon, silk, nylon or pericardium), and the heart is closed. The patient is then taken off the cardiopulmonary bypass machine, and the chest closed.
In place of direct suturing, closures of interauricular septal defects by means of a prosthesis have been disclosed. U.S. Pat. No. 3,874,388 discloses a shunt defect closure system including a pair of opposed umbrella-like elements locked together in a face to face relationship and delivered by means of a catheter, whereby a defect is closed. U.S. Pat. No. 4,836,204 discloses a double-balloon septal defect occlusion catheter used in conjunction with a surgical procedure to temporarily close septal perforations, particularly spontaneous ventricular septal perforations following acute myocardial infarction.
U.S. Pat. No. 5,192,301 discloses a deformable plug of a shape memory polymer of polynorbornene, styrene-butadiene copolymer, polyurethane, or transisoprene having a recovery temperature of 20.degree. C.-70.degree. C., and a device for closing a septal defect including the plug, a catheter and a guide wire. The plug has a flange on at least one side of the defect and is retained in the body as a "rubbery, flexible member".
There still exists a need, however, for a simple method of closing septal defects, either temporarily or permanently, with an improved plug made of a bioabsorbable material that is hardened in-situ.
The art referred to and/or described above is not intended to constitute an admission that any patent, publication or other information referred to herein is "prior art" with respect to this invention. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 C.F.R. .sctn.1.56(a) exists.